The invention relates to a device for monitoring groups of cigarettes oriented in the longitudinal direction (cigarette groups) or of other elongate articles, preferably during transport, by sensing at least one upper layer of cigarettes (top layer), a signal being triggered in the event of a missing cigarette or a defective cigarette.
In the packaging of cigarettes, it is customary to check for defects in both the individual cigarettes and a group of these (cigarette group) to be received in a pack. A first check is carried out from the front or end faces of the cigarettes (head check), specifically usually in the region of a cigarette turret following a cigarette magazine. The cigarette turret serves for forming the cigarette groups or for transferring them to a cigarette conveyor.
The further check, intended particularly for verifying that the complete number of cigarettes is present in a cigarette group, is carried out in the region of the (linear) cigarette conveyor. In this case, the upper layer of the horizontal cigarettes rotating in the conveying direction is sensed (top-layer check). This check has hitherto been executed mechanically, in particular with the use of tracer members (tracer fingers) which as a result of the transport movement of the cigarette group slide along on the upper face of the top layer of the latter. When a cigarette is missing or when there is a defective cigarette, a signal is triggered as a result of the changed relative position of a tracer member.
The abovementioned mechanical top-layer check has disadvantages. On the one hand, the cigarettes are necessarily subjected to mechanical stress. This results in soiling and often even in the destruction of individual cigarettes. Furthermore, this type of cigarette check is unsuitable for high-performance packaging machines, since the tracer members cannot follow the rapid relative movements required and execute uncontrolled jumping movements.